[joeavaerage]

Hi,
if you are using coolant you need a much bigger table top. You need sides to surround the whole machine otherwise coolant will go EVERYWHERE. I had flood coolant on my first
mini-mill but it was not particularly well thought out.........and I seemed to spend a lot of time cleaning up coolant leaks.

My new mill is vastly better, but still not as good as it should be. Hopefully sometime over the next twelve months I'll get to re-do the coolant system. I want a 100l tank, a pull-out tray filter and be able to remove the tank easily
to clean it out completely. I promise you'll have to do it every once in a while....and making it easy to do is a priority. I did my coolant tank over the weekend (annual event), took several hours, where with good design I should
be able to do it in under and hour.

Craig

[maxki]

Indeed, I tend to always plan builds to be upgradable, so my initial bench will only have a simple slab that doesn't catch chips, coolant, etc,
and I'll refrain from flood cooling, but the day I decide it's time, I'll make a "junk catching" chip pan, with the sheet metal I will have accumulated.

Nice mill BTW, I assume it's your creation, it looks well thought out !

Hi,
if you are using coolant you need a much bigger table top. You need sides to surround the whole machine otherwise coolant will go EVERYWHERE. I had flood coolant on my first
mini-mill but it was not particularly well thought out.........and I seemed to spend a lot of time cleaning up coolant leaks.

My new mill is vastly better, but still not as good as it should be. Hopefully sometime over the next twelve months I'll get to re-do the coolant system. I want a 100l tank, a pull-out tray filter and be able to remove the tank easily
to clean it out completely. I promise you'll have to do it every once in a while....and making it easy to do is a priority. I did my coolant tank over the weekend (annual event), took several hours, where with good design I should
be able to do it in under and hour.

Craig

[joeavaerage]

Hi,
flood cooling is just so much the 'night and day' difference that I sought. I use to use air-blast and oil spray, and it worked OK.

With sticky grades of aluminum (3000 series and some of the marine 5000 series) I still had trouble with chips adhering to the tool. Same with plastics. Most plastics cut well
but the chips are very inclined to adhere to the tool and wreck the job. The main requirement for any 'cooling' solution for these materials is to clear the chips away rather than
having them be re-cut and thereby adhere to the tool. Air-blast works, but flood cooling works better.

With steel its about cooling and secondarily about lubricity. Most hobbyists use high speed, low torque spindles, say 24000rpm. They are cheap and extremely useful, but bloody hopeless in steel. With steel you
need much lower speed and much higher torque. You might reasonably point out that there are many videos on YTube all running tools in steel fast.......but what you do not see is that those tools last
1/2 an hour, an hour, maybe more or maybe less....but not long enough for expensive tools.

I work on this rule of thumb:

100m/min for uncoated carbide tools in mild steel. 125m/min to 150m/min with coated carbide tools. For tough steels, eg 4340, reduce the surface speed by 25%. For stainless reduce by 50%.

All of these imply and require well directed, uninterrupted flood cooling or the tool fries up within 10 seconds to a minute.

For example I use 1/8th" Destiny Tools Raptor tools. They are just a good US brand, nothing extra special, just good, with good AlTiN coatings. I run them at 15000rpm or 147m/min,
and with steady flood cooling I get 4 to 5 hours tool life in mild steel and 6 to 8 hours if I slow it down to 12000rpm (117m/min).

If your mill is conventional, that is to say with a belt or gear driven spindle then its likely the rpm range will be low and high torque. This is good for steel. You will even get good
tool life without cooling and coated carbide tools, ,but your tool life will double or treble with well directed, uninterrupted flood cooling.

The worse thing about flood coolant is that it sprays around when you direct at a rotating tool. You may well have seen otherwise fairly conventional mills but with a large tray underneath and low walls
up to somewhat over the tool height to contain the worst of the coolant. With high speed spindles that coolant hits the tool and almost turns into a spray....and those walls need to be much higher
or even enclose the whole machine.

Craig

[joeavaerage]

Hi,
last week I was doing a job for a customer where I had to make 14 parts out of acetal. The total machine time was about six hours.

My coolant tank is only 10l, and yet through the course of the day I topped up the coolant four or maybe five times at 4l per top up.
Where does it all go? Sure I still have a few little leaks and there was some coolant on the concrete floor but I'd swear no more than 0.5l....
so I can only guess that when the coolant hits the tool and turns into spray that a larger proportion evaporates than you might think.
When I'm doing plastics I don't bother with soluble oil, that I save for metals, so its not like it was costing anything...but still is a mystery where
it all goes.

Craig